import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {

        System.out.println("Hello world!");
    }

    //最长数对链
    public int findLongestChain(int[][] pairs) {
        // 预处理
        Arrays.sort(pairs, (a, b) -> a[0] - b[0]);
        int n = pairs.length;
        int[] dp = new int[n]; // 建表
        for (int i = 0; i < n; i++) dp[i] = 1; // 初始化

        int ret = 1;
        for (int i = 1; i < n; i++) {
            for (int j = 0; j < i; j++)
                if (pairs[j][1] < pairs[i][0])
                    dp[i] = Math.max(dp[j] + 1, dp[i]);
            ret = Math.max(ret, dp[i]);
        }
        return ret;
    }


    //最⻓定差⼦序列
    public int longestSubsequence(int[] arr, int difference) {
        // 创建⼀个哈希表，在哈希表中做 dp
        Map<Integer, Integer> hash = new HashMap<Integer, Integer>(); //arr[i], dp[i]

        int ret = 1;
        for (int a : arr) {
            hash.put(a, hash.getOrDefault(a - difference, 0) + 1);
            ret = Math.max(ret, hash.get(a));
        }
        return ret;
    }
}